The present invention relates to an oscillator and, more particularly, to the structure of a shield case for an oscillator which reduces the variation in the oscillation characteristics of the oscillator ascribable to the changes in environmental conditions.
It is a common practice with an oscillator to cover a body thereof with a shield case made of brass, phosphor bronze or similar metal, so that the body may be protected against external electromagnetic fields. Therefore, stray capacitance unavoidably exists between the shield case and various parts constituting the circuitry of the oscillator. When vibration is applied from the outside to the oscillator, it causes the shield case to vibrate since the the latter is not implemented with a vibration absorbing material. The vibration of the shield case changes the physical distance between the inner periphery thereof and the component parts of the circuitry and, therefore, the stray capacitance. As a result, the externally derived vibration adversely affects the oscillation characteristics of the oscillator such as oscillation frequency, preventing the oscillator from oscillating in a stable manner.